1. Technical Field
The disclosure relates to power over Ethernet (PoE) technology and, particularly, to a powered device (PD).
2. Description of Related Art
Generally, Ethernet switches, routers, hubs, and other Ethernet powered devices (PDs) can be connected to a local power supply for continuous power. In addition, the PD can be connected to power sourcing equipment (PSE) which includes a backup battery for temporary power, which uses power over Ethernet (PoE) technology during failure of the local power supply.
PoE technology, as proposed by the Institute of Electrical and Electronics Engineers (IEEE), must comply with the IEEE 802.3af standard. Currently, when the PD is powered by the local power supply, the PSE typically functions in an idle mode. In the idle mode, the PSE continues detecting if any functioning PD is loaded thereto every two seconds, and classifies the power of the functioning PD, if detected. Then, the PSE is switched to a normal mode for a normal power supply. Accordingly, it can take as long as four seconds to resume normal power supply from the PSE. During the delay, communication via the PD is unavoidably interrupted.
Therefore, it is desirable to provide a protection circuit and a PD, which can overcome the limitations described.